Alkylbenzoic Acids Research Articles

Hydrogen bond liquid cystals formed between pentyloxy benzoic acid and alkyl benzoic acids: chemical, optical, and thermal investigations

Chemical, optical, and thermal characterization are carried out for seven hydrogen bond thermotropic liquid crystalline complexes formed between pentyloxy benzoic acid (5BAO) and p-n-alkyl benzoic acids (nBA, where n refers alkyl carbon chain length which varies from ethyl to octyl. FTIR, 1H, and 13C Nuclear Magnetic Resonance (NMR) establishes the chemical investigations. Nematic and smectic F are the mesophases observed. Polarizing Optical Microscopic (POM) studies ensures the mesophases identified. Thermal investigation using Differential Scanning Calorimeter (DSC), provides the phase transition temperatures, enthalpy values, thermal stability factor, specific heat capacity values, and thermal equilibrium of the mesogenic complexes.

Investigation on the thermal and optical properties of hydrogen bonded liquid crystalline complexes formed from hexyloxy benzoic acid and alkyl benzoic acids

Seven hydrogen bonded thermotropic liquid crystalline complexes are formed between hexyloxy benzoic acid (6BAO) and p-n-alkyl benzoic acids (nBA, where n refers alkyl carbon chain length which varies from 2 to 8) and characterized. Chemical characterization such as FTIR, 1H and 13C NMR studies are performed to confirm the hydrogen bond existence and chemical environment of the proposed molecular structure respectively. The existence of mesophases such as nematic and smectic F in the synthesized complexes are observed by Polarizing Optical Microscope (POM). The thermal analysis of this series is executed with the aid of Differential Scanning Calorimeter (DSC), which gives clear picture about the phase transition temperatures and their corresponding enthalpy values. Phase diagram is constructed with the help of the data consolidated from POM and DSC. Navard and Cox method have been implemented in estimating the order of phase transition. Specific heat capacity and light filtering action are the additional characterization techniques carried out in this described work.

Physical, chemical, optical and insulating properties of alkyl benzoic acid derivatives liquid crystal due to extension alkyl chain (CNH2N+1) length: A DFT study

Physical, chemical, optical and insulating properties of alkyl benzoic acid derivatives liquid crystal due to extension alkyl chain (CNH2N+1) length: A DFT study

Exploring the Factors which Result in Cytochrome P450 Catalyzed Desaturation Versus Hydroxylation.

The cytochrome P450 family of monooxygenase enzymes have essential biological roles involving the selective oxidation of carbon-hydrogen bonds. They can also catalyze other important metabolic reactions including desaturation to form alkenes. Currently the factors that control the partition between P450 hydroxylation and desaturation pathways are poorly defined. The CYP199A4 enzyme from the bacterium Rhodopseudomonas palustris HaA2 catalyzes the oxidation of 4-ethyl- and 4-isopropyl- benzoic acids with hydroxylation and desaturation occurring in significant quantities. Here we demonstrate that 4-cyclopropylbenzoic acid is regioselectively hydroxylated by CYP199A4 at the benzylic carbon. In contrast, the oxidation of 4-n-propylbenzoic acid by CYP199A4 results in three major metabolites: an alkene from desaturation and two hydroxylation products at the benzylic (Cα) and Cβ carbons in similar quantities. Extending the length of the alkyl substituent resulted in 4-n-butylbenzoic acid being oxidized at the benzylic position (45%) and desaturated (55%). In contrast, 4-isobutylbenzoic generated very little alkene (5%) but was hydroxylated at the benzylic position (54%) and at the tertiary Cβ position (41%). The oxidation of 4-n-propylbenzoic acid by the F298 V mutant of CYP199A4 occurred with no hydroxylation at Cβ and a significant increase in metabolites arising from desaturation (73%). The X-ray crystal structures of CYP199A4 with each substrate revealed that they bind in the active site with the alkyl substituent positioned over the heme. However, the longer alkylbenzoic acids were bound in a different conformation as was 4-n-propylbenzoic acid in the F298 V mutant. Overall, the changes in metabolite distribution could be ascribed to bond strength differences and the position of the alkyl group relative to the heme.

Strong Bathochromic Shift of Conjugated Polymer Nanowires Assembled with a Liquid Crystalline Alkyl Benzoic Acid via a Film Dispersion Process.

We present aqueous dispersions of conjugated polymer nanowires (CPNWs) with improved light absorption properties aimed at aqueous-based applications. We assembled films of a donor–acceptor-type conjugated polymer and liquid crystalline 4-n-octylbenzoic acid by removing a cosolvent of their mixture solutions, followed by annealing of the films, and then formed aqueous-dispersed CPNWs with an aspect ratio >1000 by dispersing the films under ultrasonication at a basic pH. X-ray and spectroscopy studies showed that the polymer and liquid crystal molecules form independent domains in film assemblies and highly organized layer structures in CPNWs. Our ordered molecular assemblies in films and aqueous dispersions of CPNWs open up a new route to fabricate nanowires of low-band-gap linear conjugated polymers with the absorption maximum at 794 nm remarkably red-shifted from 666 nm of CPNWs prepared by an emulsion process. Our results suggest the presence of semicrystalline polymorphs β1 and β2 phases in CPNWs due to long-range π–π stacking of conjugated backbones in compactly organized lamellar structures. The resulting delocalization with a reduced energy bang gap should be beneficial for enhancing charge transfer and energy-conversion efficiencies in aqueous-based applications such as photocatalysis.

Investigation on two homologus series of ferroelectric hydrogen bond liquid crystals derived from camphoric acid and alkyloxy/alkyl benzoic acids

Two ferroelectric series comprising of 12 mesogens are investigated. In the first homologous series, Camphoric acid abbreviated as CA which is a ferroelectric ingredient, formed hydrogen bonds with benzoic acids with oxygen atom abbreviated as nBAO. The carbon chain of the benzoic acids varied from 5 to 12 atoms. Thus eight homologous members are synthesized. This mesogenic homologous series is represented as CA+nBAO. Similarly, Camphoric acid formed hydrogen bonds with alkyl benzoic acids abbreviated as nBA. The carbon number of the benzoic acids varied from 5 to 8. This mesogenic homologous series is represented as CA+nBA. Phases observed includes a new phase variant Smectic X*, and conventional phases C*, I* and G*. DSC thermograms exposed the Tc and corresponding ΔH magnitudes. Dielectric relaxations in smectic C* are discussed for a selected mesogen. The existence of oxygen in CA+nBAO facilitated presence of abundance poly phase morphism.

Synthesis of Octyl-Quaternary Ammonium Mixed-Mode Stationary Phase by Vapor Deposition Approach and Its Application in Compound Preparation Separation

An octyl-quaternary ammonium (Sil-C8-QA)-modified silica stationary phase was prepared by a two-step vapor deposition method which can substantially reduce the consumption of toxic organic solvents. The structure of the dual-functional ligands stationary phase was characterized by Fourier transform infrared spectroscopy and solid-state 13C CP/MAS NMR. Following elemental analysis, the surface density of octyl and quaternary ammonium bonding amount is 2.13 µmol m−2 and 0.77 µmol m−2, respectively. The efficiency and selectivity of the two-ligand phases were compared with two sole functional ligand phases: quaternary ammonium (Sil-QA)- and octyl-modified silica (Sil-C8). Chromatographic evaluation demonstrated a mixed-mode reversed-phase/anion-exchange retention property on the Sil-C8-QA column. The retention behavior of a homologous series of alkylbenzoic acids on the synthesized phase was systematically studied by changing the pH, ionic, and solvent strength of the mobile phase. A well-established mixed-model mechanism was confirmed. The Sil-C8-QA phase can predominantly enhance the retention of acidic drugs and improve their selectivity. It was also successfully applied to the simultaneous separation and determination of three kinds of compound preparations with large differences in component polarity.

Quantum and Thermodynamic Estimation of Mesostate Behaviour of Alkyl Benzoic Acids in Dielectric Medium: Comparative Study

Quantum and thermodynamic estimation of mesostate behaviour of p-n-alkyl benzoic acid with pentyl (PBA), hexyl (HBA) groups has been studied in dielectric medium (benzene). The complete neglect differential overlap (CNDO/2) method has been implemented for the charges, dipole moment and its components analysis. The long-range intermolecular interactions have been examined using the modified Rayleigh–Schrodinger perturbation method coupled with multicentred multipole expansion method. For understanding the short-range interactions, a ‘6-exp’ potential function has been used. The interaction energy values have been used to estimate the probability of each configuration in a dielectric medium (benzene) using the Maxwell–Boltzmann formula at room temperature (300 K) and at nematic–isotropic transition temperatures. Thermodynamic view has been presented based on Helmholtz free energy and entropy. A correlation has been made between quantum statistical and thermodynamic data to estimate the mesostate behaviour of the title molecules.

Production of Terephthalic Acid from Corn Stover Lignin

Funneling and functionalization of a mixture of lignin-derived monomers into a single high-value chemical is fascinating. Reported herein is a three-step strategy for the production of terephthalic acid (TPA) from lignin-derived monomer mixtures, in which redundant, non-uniform substitutes such as methoxy groups are removed and the desired carboxy groups are introduced. This strategy begins with the hydro-treatment of corn-stover-derived lignin oil over a supported molybdenum catalyst to selectively remove methoxy groups. The generated 4-alkylphenols are converted into 4-alkylbenzoic acids by carbonylation with carbon monoxide. The Co-Mn-Br catalyst then oxidizes various alkyl chains into carboxy groups, transforming the 4-alkylbenzoic acid mixture into a single product: TPA. For this route, the overall yields of TPA based on lignin content of corn stover could reach 15.5 wt %, and importantly, TPA with greater than 99 % purity was obtained simply by first decanting the reaction mixture and then washing the solid product with water.

Investigations on smectic X* and re-entrant smectic C* orderings in hydrogen bonded ferroelectric liquid crystals

Two homologous series of hydrogen bonded ferroelectric liquid crystal (HBFLC) series have been isolated. One mole of ferroelectric Dextro tartaric acid (DTA) is mixed with 2 mol of p-n-alkyloxy benzoic acid (BAO) to obtain homologues of DTA + nBAO. Eight mesogens are isolated by varying the carbon number from pentyloxy to dodecyloxy viz., DTA + 5BAO to DTA + 12BAO. Similarly 1 mol of ferroelectric Dextro tartaric acid (DTA) is mixed with 2 mol of p-n- alkyl benzoic acid (BA) to obtain homologues of DTA + nBA. Seven mesogens are isolated by varying the carbon number from pentyl to dodecyl viz., DTA + 3BA to DTA + 8BA. Spectroscopic characterization (FTIR, 1H and 13CNMR) for all the 14 mesogens indicate the formation of hydrogen bond in HBFLC. Optical textures are recorded in various phases. An interesting observation is the finding of parachromatism in cholesteric phase. In addition to the conventional phases, two new smectic orderings viz., smectic X* and re-entrant smectic C* have been characterized. The textures of smectic X* exhibits a worm like textures while that of smectic C* is broken focal conic and the transition from smectic X* to re-entrant smectic C*. Smectic X* is observed to be sandwitched between cholestric and smectic C*. The x-ray study of smectic X* confirm it to be a smectic ordering. Measurments of tilt angle, light filtering and dielectric relaxation studies have been performed in this new smectic ordering. A new smectic ordering labeled as re-entrant smectic C* has been identified and characterized. Data of dielectric relaxation, magnitude of tilt angle in this phase confirm this phase is distinctly different from conventional smectic C*. Re entrant Smectic C* and Smectic X* are observed in higher homologues of DTA + nBAO where ‘n’ varies from 8 to 12.

Design, synthesis and characterization of hydrogen bonded thermotropic liquid crystals

ABSTRACTA homologous series of seven linear hydrogen bonded thermotropic liquid crystals are isolated from p-n-octyloxy benzoic acid (8BAO) and p-n alkyl benzoic acids (nBA, where n varies from 2 to 8). In all the seven complexes, hydrogen bonding is a result of complementary proton-donor and electron-acceptor pairs derived from carboxylic acids of 8BAO and nBA. Spectroscopic characterization such as Fourier Transform Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (1HNMR, 13CNMR) are performed for all the seven complexes to confirm the intermolecular hydrogen bonding and the nature of chemical environment respectively. Seven mesogen are examined by Polarizing Optical Microscope (POM) for identification of the phase polymorphism through standard textures. Transition temperatures and corresponding enthalpy values of the individual mesogenic phases are experimentally obtained from the analysis of the respective Differential Scanning Calorimetry (DSC) thermograms. Phase diagram of this homologous series is constructed based on the data of transition temperatures, further qualitative analysis of the phase abundance is discussed. Thermal stability factor for each of the mesogenic phase has been determined. Order of phase transition is experimentally obtained by Navard and Cox technique. Specific heat for each phase transition of individual complexes is derived from the DSC data. Change of color of the texture with temperature in the same phase is referred as parachromatism and is observed in nematic phase of two mesogens.

Nanowires of amorphous conjugated polymers prepared via a surfactant-templating process using an alkylbenzoic acid

Abstract Conjugated polymer nanowires have recently attracted attention as new organic photocatalysts with improved photoexcited charge-carrier lifetime capable of efficient energy harvesting from sunlight. However, most methods to prepare the nanowires have focused on crystalline conjugated polymers, thereby limiting the number of usable polymer structures. In this study, we present a method for preparing nanowires of amorphous conjugated polymers to expand their applicability as photocatalysis. We demonstrate a nanowire fabrication process that utilizes an alkylbenzoic acid. At a specific concentration, the amphiphilic alkylbenzoic acid forms wire morphologies when its organic solution is added to an aqueous solution, partitioning the organic solution inside the wires and the outside aqueous solution. When the amorphous conjugated polymer in the organic solution is added, the conjugated polymers are located in the wires and form conjugated polymer nanowires upon removal of the organic solvent.

Comparison of mesomorphic properties exhibited by linear hydrogen bonded thermotropic liquid crystals

ABSTRACTTwo linear hydrogen-bonded liquid crystal homologous series have been isolated in the present investigation and compared. Palmitic acid is chemically bonded with alkyloxy benzoic acids, and alkyl benzoic acids to yield 15 mesogenic complexes. The formation of inter molecular hydrogen bonding is confirmed by Fourier transform infrared spectroscopy (FTIR). Phase polymorphism exhibited by the two linear homologous series is evinced by various textural observations made through polarizing optical microscopic (POM) studies. Differential scanning calorimetry (DSC) studies revealed the transition temperatures and the corresponding enthalpy values exhibited by the individual phases. Phase diagrams has been constructed through POM and DSC data. Thermal equilibrium, thermal stability factor, and order of phase transition data are obtained from DSC study. Influence of oxygen atom attached/detached to the rigid chemical moiety toward the properties of the homologous series is discussed. Light filtering action of the nematogens at different temperatures is also conferred.

Synthesis of liquid crystals based on hydrogen-bonding of 4-(Octyloxy)benzoic acid with 4-alkylbenzoic acids

ABSTRACTA molecular recognition process has been used to form new mesogenic molecular structures, where intermolecular hydrogen bonding occurs between 4-(octyloxy)benzoic acid (8BAO) and four 4-alkylbenzoic acids (nBAs, n = 2, 5, 6, 7). The synthesis of these complexes has been attained by resorting to mechanochemistry. The resulting materials have been characterized by polarizing optical thermal microscopy, differential scanning calorimetry, vibrational spectroscopy, X-ray powder diffraction, and 1H NMR relaxometry. All the elements of the series show the formation of a mesophase. For one of the complexes, its electro-optical properties have also been assessed, resulting comparable to those of other widely used liquid crystals.

Investigations on Hydrogen-Bonded Liquid Crystals Formed by P-N Alkyl Benzoic Acids and Dodecane Dicarboxylic Acids

ABSTRACTA novel homologous series of hydrogen-bonded liquid crystals (HBLC) have been investigated. These Hydrogen bonds are formed between p-n dodecane dicarboxylic acid (DDC) and various p-n-alkyl benzoic acids (nBA), the present homologous series is referred as DDC + nBA. Seven complexes formed in the present homologous series are characterized by Fourier Transform Infrared spectroscopy (FTIR), Polarizing Optical Microscopy (POM) and Differential Scanning Calorimetry (DSC). Hydrogen bond formation is confirmed by FTIR. Textures observed in DDC + nBA are compared with the standard textures for phase identification. Characteristic phase like nematic, smectic F and smectic G are identified. Odd–even effect is observed in phase transition temperatures and corresponding enthalpy values at isotropic to nematic phase. Phase diagram is constructed from POM and DSC data. The effect of oxygen is discussed with respect to DDC + nBA and DDC + nOBA series. Quantitative treatment for the phase growth is discussed. Light filtering action at various temperatures in nematic phase is also studied.

English

In this paper, thermo optical properties of homologous series of hydrogen bonded liquid crystals: p-n alkyl benzoic acid (nBA): heptyl p - hydroxybenzoate (7HB) (where n=5 to 10) have been investigated by means of applying Image analysis technique in conjunction with Polarizing Optical Microscope. Textures of liquid crystal complexes are captured. The changes in textural features as a function of temperature are useful to compute the thermo optical properties. These microscopic textures are analysed using MATLAB software. The investigated thermo optical parameters are optical transmission, Absorption coefficient, Phase retardation, birefringence and order parameter. Experimentally, this is a simple technique to observe the behaviour of the optical parameters of different liquid crystals as a function of temperature

Self-assembled liquid crystals by hydrogen bonding between bipyridyl and alkylbenzoic acids: solvent-free synthesis by mechanochemistry

A series of thermotropic hydrogen-bonded liquid crystalline structures based on 4,4′-bipyridyl and aliphatic carboxylic acids was prepared by a mechanosynthesis technique. This series was characterised by polarising optical microscope, differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction and 1H NMR relaxometry experimental techniques. In these complexes, the bipyridyl component, a non-mesogenic substance by itself, acts as a double H-bond acceptor, whereas the alkylbenzoic acid acts as a H-bond donor, in a 1:2 proportion. The so-formed complexes exhibit mesophases that are not observed by the single components. A characteristic phase (smectic A) is identified and shown to be affected by the alkyl chain length. The isotropisation temperature is increased by the supramolecular aggregation through the H-bonds.

Description of gas-phase ion/neutral interactions in differential ion mobility spectrometry: CV prediction using calibration runs.

Differential ion mobility spectrometry (DMS) coupled to mass spectrometry is increasingly used in both quantitative analyses of biological samples and as a means of removing background interferences for enhanced selectivity and improved quality of mass spectra. However, DMS separation efficiency using dry inert gases often lacks the required selectivity to achieve baseline separation. Polar gas-phase modifiers such as alcohols are therefore frequently employed to improve selectivity via clustering/declustering processes. The choice of an optimal modifier currently relies on trial and error experiments, making method development a tedious activity. It was the goal of this study to establish a means of CV prediction for compounds using a homologous series of alcohols as gas-phase modifiers. This prediction was based on linear regression of compensation voltages of two calibration runs for the alcohols with the lowest and the highest molecular weights and readily available descriptors such as proton affinity and gas phase acidity of the modifier molecules. All experiments were performed on a commercial quadrupole linear ion trap mass spectrometer equipped with a DMS device between electrospray ionization source and entrance quadrupole lens. We evaluated our approach using a homologous series of 4-alkylbenzoic acids and a selection of 23 small molecules of high chemical diversity. Predicted CV values typically deviated from the experimentally determined values by less than 0.5V. Several test compounds changed their ion mobility behavior for the investigated gas phase modifiers (e.g., from type B to type A) and thus could thus not be evaluated.

Image analysis method to study electro-optic parameters of nematogens

This paper demonstrated the image analysis technique for the investigation of electro-optic behaviour of homogeneously aligned nematic liquid crystals p-n alkyl benzoic acids (nBA) where n = 5 and 6 under the application of direct current (DC) electric field. Textures of the liquid crystals in the mesophase region of particular temperature were recorded in three monochromatic image planes at the wavelengths of 635 (red), 530 (green) and 475 nm (blue) as a function of applied DC voltage. Electro-optic properties such as transmittance, birefringence, phase retardation and contrast ratio were measured by analysing the optical intensities of the recorded textures using MATLAB software. The changes in the textural features and formation of new textures as a function of voltage provided information for better understanding of the electro-optic characteristics of liquid crystals. Results of this study were compared with the data of the other standard techniques: laser source (633 nm) experiment and United Detector Technology (UDT) sensor of model UV- 35P silicon photo diode which uses white light as source and filters the wavelengths using three colour filters of wavelengths 635, 530 and 475nm.

Thermal Analysis of Supramolecular Hydrogen-Bonded Liquid Crystals Formed by Nonyloxy and Alkyl Benzoic Acids

A novel series of supramolecular hydrogen-bonded complexes (supramolecular hydrogen-bonded liquid crystal, SMHBLC) has been isolated from equimolar ratios of p-n-nonyloxy benzoic acid (9BAO) and seven p-n-alkyl benzoic acids (nBA) whose carbon number varied from ethyl to octyl. Complementary hydrogen bonds are formed between them. They have been investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and further these data are utilized for the construction of phase diagram. Characteristic textures of the orthogonal and tilted phases have been recorded and compared. A new smectic ordering referred to as smectic X is characterized by various techniques. Odd–even effects are evinced in transition temperatures. The order of the transitions is distinguished by thermal analysis. The magnitude of experimental optical tilt angle in smectic C of all the homologs is fitted to a power law and the value of exponent is found to concur with the mean field theory predicted value.